1. Field of the Invention
The present invention relates to an improved variable intake apparatus for an in-line four-cylinder internal combustion engine which can obtain a high intake air charging efficiency and a high output torque over a wide engine speed range of the internal combustion engine from low to high engine speed ranges.
2. Description of the Related Art
Conventionally, various types of intake apparatuses have been proposed which are designed to make use of intake air pressure-wave pulse generated in air intake passages connecting to communicate with the respective cylinders of a multi-cylinder internal combustion engine, so as to obtain an extra charging effect by elevating the pressure at inlet ports of respective cylinders of the engine toward a latter half of an intake stroke in the respective cylinders.
For example, the length and/or volume of intake pipes is varied in response to the speed of an internal combustion engine so as to obtain an inertial supercharging effect and a resonance supercharging effect in supercharging intake air. With a suitable combination thereof, the intake air charging efficiency is highly maintained over a wide engine speed range from low to high engine speed ranges, whereby the output torque of the internal combustion engine is aimed at being improved.
In in-line four-cylinder internal combustion engines, there has been proposed a variable intake apparatus in which the length of air intake passages communicating with respective cylinders of an engine varies in triple stages such as for the low engine speed range, intermediate engine speed range and high engine speed range so as to obtain a high intake air charging efficiency to thereby aim at improving the output torque of the engine (JP-B-7-30698). Further, three has been proposed a variable intake apparatus in which junction portions where air intake passages communicating with respective cylinders of an engine are arranged in such a manner that the air intake passages are connected to the cylinders which do not have successive intake strokes are made to function as a resonating chamber, in which resonating pipes are provided on upstream sides of the resonating chambers so as to connect thereto along a direction in which the cylinders are arranged, and in which a collecting portion is provided upstream of the pair of resonating pipes. And, in the latter variable intake apparatus, the communication between the pair of resonating chambers is blocked off and established for the low and intermediate engine speed range and the high engine speed range of the internal combustion engine so as to obtain a high intake air charging efficiency using resonating and inertial supercharging effects, to thereby aim at improving the output torque of the engine (JP-A-10-73024).
However, with the former variable intake apparatus, two air intake control valves are needed which operate individually, and this increases the number of components used in and weight of the intake apparatus, resulting a problem that the engine is disadvantageous with respect to space. In addition, in the case of the latter variable intake apparatus in which the resonating supercharging effect is used in the low and intermediate engine speed range, the resonating chambers, resonating pipes and collecting chamber need to be provided, and the provision of the pair of resonating pipes increase the size of the intake apparatus itself in the direction in which the cylinders are arranged, this making the engine disadvantageous with respect to the space in the direction in which the cylinders are arranged. Moreover, it has been difficult to obtain a flat intake air charging efficiency at a narrow portion between the low and intermediate engine speed range and the high engine speed range.
There are variable intake apparatuses employing a rotary valve in internal combustion engines (JP-7-253063). However, the rotary valve used in such variable intake apparatuses is such that the rotary valve is switched over in double stages in response to low and high engine speed ranges of the internal combustion engine and that only sealing between adjacent air intake passages is intended by effecting sealing between the adjacent air passages only with simple O-type seal rings.
An object of the invention is to provide a variable intake apparatus for an in-line four-cylinder internal combustion engine which can solve the problems inherent in the conventional in-line four-cylinder internal combustion engines so as to obtain a high intake air charging efficiency over a wide range of engine speeds such as from the low engine speed range to the high engine speed range of an internal combustion engine to thereby obtain a high output torque and which can reduce the number of components used therein and simplify the construction thereof so as to require less space for provision thereof.
To solve the above object, there is provided a variable intake apparatus for an in-line four-cylinder internal combustion engine, characterized in that:
four air intake passages which are independent from each other and which connect to and communicate with respective cylinders of the in-line four-cylinder internal combustion engine, respectively, at one ends thereof and a single intake air collecting chamber at the other ends thereof are arranged sideways in line with each other in a direction in which the cylinders of the internal combustion engine are arranged; in that
the air intake passages are curved so as to wind inwardly, and the intake air collecting chamber is disposed in an internal space in the curved portion of the air intake passages; in that
a rotary valve is provided in such a manner that a part of the outer circumference thereof projects into intermediate portions along the length of the air intake passages in an arc-like fashion; in that
the rotary valve comprises control means that can be switched over in triple stages at equal intervals in response to the rotational speed of the internal combustion engine; in that
the rotary valve establishes or cuts off a communication between the air intake passages which are adjacent to each other or between each of pairs of air intake passages connecting to and communicating with respective cylinders of pairs of cylinders which do not have successive intake strokes, at the one ends thereof; and in that
the control means is constructed such that at a low engine speed range of the internal combustion engine, a communication is cut off between the air intake passages which are adjacent to each other, at an intermediate engine speed range of the engine, a communication is established between each of the pairs of air intake passages connecting to and communicating with the respective cylinders of the pairs of cylinders which do not have successive intake strokes at one ends thereof, and at a high engine speed range thereof, a communication is established between the air intake passages which are adjacent to each other.
According to the invention, the four air intake passageways are provided so as to be arranged sideways in line with each other which are independent from each other and which connect to and communicate with respective cylinders of an in-line four-cylinder internal combustion engine, respectively, at one ends and a single intake air collecting chamber at the other ends thereof. As a result, the respective air intake passageways in no case intersect with each other, and the intake apparatus (an intake manifold) can be formed compact in the direction in which the cylinders of the engine are arranged, providing a good space efficiency. Additionally, the equalization of the lengths of the respective air intake passageways can be eased.
In addition, provided between the intermediate portion along the length of the four air intake passageways which are independent from each other and the intake air collecting chamber is the rotary valve which is adapted to establish or cut off a communication in a shortcut fashion between the respective air intake passageways and the intake air collecting chamber, and the rotary valve comprises the control means that can be switched over in triple stages at equal intervals in response to the rotational speed of the internal combustion engine, the control valve being adapted to control and switch over the rotary valve such that, at a low engine speed range of the internal combustion engine, a communication is cut off between the air intake passageways which are adjacent to each other, at an intermediate engine speed range of the engine, a communication is established between each of the pairs of adjacent air intake passageways connecting to and communicating with the respective cylinders of the pairs of cylinders which do not have successive intake strokes at one ends thereof, and at a high engine speed range thereof, a communication is established between the air intake passageways which are adjacent to each other and a communication is also established in a shortcut fashion between the respective air intake passage ways and the intake air collecting chamber.
As a result, at the low engine speed range of the internal combustion engine, the intake air collecting chamber functions as a portion which is open to the atmosphere and hence becomes a reverse chamber where intake pressure wave pulses are reversed, whereby the intake pressure wave pulse inside the long air intake passageways between the combustion chambers and the intake air collecting chamber which has a low natural frequency is tuned to the long opening and closing cycle of the inlet valve based on the low engine speed of the engine to thereby obtain a high inertial supercharging effect, whereby a high intake air charging efficiency can be obtained for each cylinder, thereby making it possible to improve the output torque of the engine.
Moreover, at the intermediate engine speed range, the air intake passageway portions upstream of the communicating portion between the pairs of adjacent air intake passageways connecting to and communicating with the cylinders which do not have successive intake strokes at one ends thereof constitute a resonating system for each of the pairs of cylinders, whereby intake pressure waves remain unreversed in the respective air intake passageways and the communicating portion and can be propagated for the following intake stroke in the other cylinder of the same pair of cylinders, allowing a high resonating supercharging effect to be obtained, so that a high intake air charging efficiency can be obtained for each cylinder of the pair of cylinders which does not have successive intake strokes to thereby improve the output torque, thus making it possible to compensate for drops in intake air charging efficiency and output torque at the intermediate portion between the low and high engine speed ranges.
Furthermore, at the high engine speed range, the communicating chamber between the adjacent air intake passageways functions as the portion which is open to the atmosphere, and the communicating chamber becomes the reverse chamber where intake pressure wave pluses are reversed, whereby the intake air pressure wave pulse in the short air intake passageways extending from the combustion chambers to the communicating chamber which has a high natural frequency is tuned to the short opening and closing cycle of the intake valve based on the high rotational speed of the engine to thereby obtain a high inertial supercharging effect, and this allows a high intake air charging efficiency to be obtained for all the cylinders, thereby making it possible to improve the output torque of the engine. Thus, the high intake air charging efficiency and the high output torque can be obtained over a wide range of engine speed range from the low engine speed range to the high engine speed range.
In addition, at the high engine speed range, since the respective air intake passageways and the intake air collecting chamber are caused to communicate with each other in a shortcut fashion via the rotary valve, the respective air intake passageway portions (long air intake passageway portions)upstream of the communicating chamber between the adjacent air intake passageways are made thinner, and even if the low engine speed range is shifted down towards a lower engine speed side, an intake air flow rate which is required at the high engine speed range can be acquired sufficiently, whereby the intake apparatus can be formed more compact.
Moreover, since the high intake air charging efficiency and the high output torque can be obtained over the wide engine speed range which ranges from the low engine speed area to the high engine speed area by controlling to switch over the rotary valve provided between the intermediate portion along the length of the four air intake passageways which are independent from each other and the intake air collecting chamber in such a manner as to switch it over in triple stages at regular intervals in response to the rotational speed of the internal combustion engine, the number of components such as valves and actuators can be reduced, whereby the production costs can be reduced, the construction and weight of the apparatus can be simplified and reduced, respectively. This eases the provision of the variable intake apparatus for an in-line four-cylinder internal combustion engine which requires less space for installation thereof. In addition, since with the rotary valve, the valve body and the shaft portion thereof do not protrude into the air intake passageways, there is no risk of the intake resistance being increased.